xfrm_user: validate XFRM_MSG_NEWAE incoming ESN size harder

Orabug: 25805996
CVE: CVE-2017-7184

Kees Cook has pointed out that xfrm_replay_state_esn_len() is subject to
wrapping issues.  To ensure we are correctly ensuring that the two ESN
structures are the same size compare both the overall size as reported
by xfrm_replay_state_esn_len() and the internal length are the same.

Signed-off-by: Andy Whitcroft <apw@canonical.com>
Acked-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit f843ee6dd019bcece3e74e76ad9df0155655d0df)
Signed-off-by: Brian Maly <brian.maly@oracle.com>

diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index 1c1b9ed947192c1e8ab56d9a17c3010eab82f64a..2dc882637cdf32f2073182cd51eb831cb3438670 100644 (file)
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -386,7 +386,11 @@ static inline int xfrm_replay_verify_len(struct xfrm_replay_state_esn *replay_es
        up = nla_data(rp);
        ulen = xfrm_replay_state_esn_len(up);
 
-       if (nla_len(rp) < ulen || xfrm_replay_state_esn_len(replay_esn) != ulen)
+       /* Check the overall length and the internal bitmap length to avoid
+        * potential overflow. */
+       if (nla_len(rp) < ulen ||
+           xfrm_replay_state_esn_len(replay_esn) != ulen ||
+           replay_esn->bmp_len != up->bmp_len)
                return -EINVAL;
 
        if (up->replay_window > up->bmp_len * sizeof(__u32) * 8)